Steel aluminum, tin or other metals are typically rolled upon a mandrel as a final phase of production. In the steel industry, these mandrels typically have a diameter of 24 or 20 inches, while in the aluminum industry that diameter typically is 16, 20, or 24 inches. The coils, are quite heavy, for example, steel coils generally weighing 60,000 up to 80,000 pounds. To transport or maneuver the coils about the mill and following their delivery to customers, cranes such as overhead cranes having a generally L-shaped or C-shaped engaging implement or a truck with a boom are employed. Typically, the engaging implement incorporates a tong or tongue which slides inside the center region of the coil and engages it for lifting. As is apparent, with the weight at hand, without some protection, the inner layers of the coil as well as the outer edges generally would be damaged. Being highly conscientious with respect to the yield of metal purchased, customers require that such damage be avoided. As a consequence, at the production mill or processor, the multi-layer coils are prepared for crane handling and shipment by the placement of flanged protectors against each coil side which are structured to protect both the edges of the metal and the internal layers of the sheet metal. Generally with this placement procedure, two mill laborers hold the coil protectors in place and they are strapped in place, or, a somewhat elaborate wrapping machine employing a shuttle will wrap both coil and the manually retained protectors with a paper or shrink wrap covering.
Currently utilized coil protectors are, for the most part, fabricated from plastic, and in view of the rigorous environment in which they are used, see only minimal reuse. While plastic recycling procedures have been promulgated, the cost of the protective devices is sought to be controlled through resort to minimizing their weight, i.e., material cost, while maintaining their capability for assuring metal coil integrity. Coil protector cost also is impacted by the cost of their shipment to the coil forming facilities. The protectors necessarily are relatively large and bulksome. To achieve a cost control over their transportation it is desirable that they be stackable prior to packaging and shipping. Such a stacking capability improves the efficiency of both their trucking to coil production facilities and their practical storage when at the site of the user. Practical coil protector stacking should provide a structurally stable column or stack, of no less than about 50 or 60 devices, preferably more, having a height extending within highway transportation regulatory authority mandated limitations.
In the course of producing metal coils, some variations in their open internal diametric extent may be expected. Tolerance variations also will be experienced in the production of plastic coil protectors, which is usually carried out utilizing injection molding procedures. Thus, the design of the protectors must be such as to accommodate tolerance-based variations in the internal diameters of the coils themselves, as well as practical or unavoidable variations experienced in the dimensions of the plastic protectors themselves. Accordingly, coil protector designs must be capable of assuring a proper union with the protected metal coil, as well as assuring that the protectors remain stackable for packaging and shipping purposes.